Measurement method and measurement device for field uniformity of microwave resonant cavity

Abstract

The invention discloses a method and a device for measuring field uniformity of a microwave resonant cavity, according to a non-resonant perturbation theory, before perturbation and after perturbation, an electromagnetic field at a corresponding position in a space is changed, the change is reflected to a reflection coefficient S11 of the electromagnetic field, and the S11 is a quantity which can be detected by a vector network analyzer. Therefore, the S11 value of the electromagnetic field before and after perturbation can be measured by using the vector network analyzer to judge the change amount of the electromagnetic field so as to obtain the delta S11 value, and the processing precision of the to-be-detected device is judged according to the consistency of the delta S11.

Description

Technical Field

[0001] The invention relates to the application field of klystron technology, and in particular to a method and a device for measuring the uniformity of a microwave resonant cavity field. Background Art

[0002] The klystron structure is an electric vacuum device that generates microwave power, mainly including electronic cavity, input cavity, cluster cavity, output cavity and collector, etc. The input cavity and cluster cavity work in the microwave band, interact with electrons at high frequency, and accelerate and cluster the electron beam.

[0003] The processing and tuning of the input cavity and cluster cavity are important processes to ensure that the klystron works at the rated power, especially for the multi-injection klystron chambers in the C and X bands. The nose cone should be consistent after fine processing. However, in actual processing, due to the existence of processing errors, the traditional method is to measure the fine processing size with a ruler, but the influence of the nose cone structure itself makes the measurement difficult.

[0004] Therefore, there is an urgent need to provide a method and device for measuring the uniformity of the microwave resonant cavity field. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method and device for measuring the uniformity of a microwave resonant cavity field. According to the non-resonant perturbation theory, the electromagnetic field at the corresponding position in the space will change before and after the perturbation, and this change will be reflected in the reflection coefficient S of the electromagnetic field. 11 , and S 11 This is another quantity that can be detected by a vector network analyzer. Therefore, we can use a vector network analyzer to measure the S of the electromagnetic field before and after the perturbation. 11 value to determine how much the electromagnetic field has changed, and then obtain ΔS 11 Value, according to ΔS 11 The consistency of the test results is used to judge the processing accuracy of the device under test.

[0006] The technical solution of the present invention is: a method for measuring the uniformity of a microwave resonant cavity field, comprising the following steps:

[0007] Step 1, selecting a suitable perturbator according to the size of the device under test, the device under test is composed of a plurality of beam channels, and the beam channels are composed of a nose cone hole, a nose cone gap and a drift tube;

[0008] Step 2: Start the vector network analyzer and perform microwave calibration. The vector network analyzer is connected to the probe through a test connection line, and the probe is placed in the nose cone hole of the device under test through a probe tooling;

[0009] Step 3: Use a vector network analyzer to read the parameter S of the device under test at the operating frequency when no perturbation body is placed.11,u ;

[0010] Step 4: Place the perturbation body and the perturbation body tooling into the nose cone gap of the device under test, and use a vector network analyzer to read the parameter S of the device under the operating frequency when the perturbation body is placed. 11,p ;

[0011] Step 5: Before and after the perturbation, the electromagnetic field at the corresponding position in the space will change, and this change will be reflected in the reflection coefficient S of the electromagnetic field. 11 value;

[0012] By comparing the ΔS of the electromagnetic field before and after the perturbation in step 3 and step 4 11 Value, to judge the change of electromagnetic field;

[0013] Step 6: When multiple ΔS 11 When the consistency of ΔS is greater than 95%, the device under test is judged to meet the requirements; when one of the ΔS 11 When the consistency is less than 95%, it is determined that the processing of the device under test does not meet the requirements.

[0014] Furthermore, in step 1, the perturbation body is made of metal material.

[0015] Furthermore, in step 2, the probe fixture is made of polytetrafluoroethylene material to fix the probe in the cavity of the nose cone hole.

[0016] Furthermore, the probe and the nose cone hole maintain the same axial direction.

[0017] Furthermore, in step 5, the relationship between the change of the electromagnetic field of the device under test before and after being perturbed is as follows:

[0018] ΔS 11 =S 11,p (ω)-S 11,u (ω)=-jω[k e E 2 -k m H 2 ] / P in

[0019] S 11,p , S 11,u are the reflection coefficients before and after the perturbation, respectively;

[0020] ΔS 11 is the difference of the electromagnetic field reflection coefficient before and after the perturbation;

[0021] P in is the average microwave power entering the resonant cavity;

[0022] k e , k mare the shape factors associated with the perturbator, respectively;

[0023] ω is the angular frequency;

[0024] E and H represent the change in electric field and magnetic field at that point, respectively.

[0025] Furthermore, when the perturbation body is a cylindrical structure, ΔS 11 Mainly determined by the electric field component. When the measured electric field is higher than the design value, the nose cone gap is reserved to be shorter, and when the measured electric field is lower than the design value, the nose cone gap is reserved to be longer; or

[0026] When the perturbation body is a circular ring structure, ΔS 11 Mainly determined by the magnetic field component. When the measured magnetic field is lower than the design value, the nose cone gap is reserved to be shorter, and when the measured magnetic field is higher than the design value, the nose cone gap is reserved to be longer.

[0027] Furthermore, in step 6, the consistency is multiple ΔS 11 Respectively at multiple ΔS 11 compared with the average value.

[0028] A test device for microwave resonant cavity field uniformity, comprising a vector network tester, a test connection line, a probe and a probe tooling, a device to be tested, a perturbation body and a perturbation body tooling;

[0029] The probe is assembled in the nose cone hole of the device under test through a probe tool;

[0030] The perturbation body is assembled in the nose cone gap of the device under test through a perturbation body tooling;

[0031] The vector network tester is connected to the probe via the test connection line.

[0032] Furthermore, the perturbation body is a metal material with a cylindrical, annular or cage-like structure.

[0033] Furthermore, the probe fixture and the perturbation body fixture are respectively coaxially arranged with the drift tube.

[0034] The beneficial technical effects of the present invention are:

[0035] A resonant cavity of a multi-injection klystron usually operates in the fundamental mode TM01, and the resonant cavity is composed of multiple beam channels, namely, a nose cone hole, a nose cone gap and a drift tube.

[0036] Ideally, the processing of these beam channels is exactly the same, so the electromagnetic field distribution formed by the resonant cavity is also exactly the same on these beam channels. The changes in the electromagnetic field that we can make by placing the same perturbation body at the corresponding nose cone gap position of each beam channel should also be consistent, that is, the S11 The changing values ​​of the parameters should also be consistent.

[0037] On the contrary, if any beam channel is processed inconsistently with other beam channels, the change in the field caused by placing the perturbation body at the corresponding nose cone gap position of the beam channel will be different from the change caused by placing it in other beam channels.

[0038] This difference can be seen through S 11 The difference in the parameter change value is reflected. Therefore, the reflection coefficient S before and after the perturbation body is placed can be measured. 11 The changes in the electromagnetic field of the multi-beam klystron resonant cavity are evaluated.

[0039] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0041] Figure 2 It is a schematic diagram of the structure of the probe and the probe tooling and the perturbation body and the perturbation body tooling of the present invention being assembled on the device to be tested;

[0042] Figure 3 This is the actual test data diagram of Example 1 of the present invention:

[0043] Among them, Figure a is the reflection coefficient at the frequency point of 1942.43MHz before interference;

[0044] Figure b is the reflection coefficient at the same frequency point of drift tube No. 1 after interference; Figure c is the reflection coefficient at the same frequency point of drift tube No. 2 after interference; Figure d is the reflection coefficient at the same frequency point of drift tube No. 3 after interference; Figure e is the reflection coefficient at the same frequency point of drift tube No. 4 after interference; Figure f is the reflection coefficient at the same frequency point of drift tube No. 5 after interference; Figure g is the reflection coefficient at the same frequency point of drift tube No. 6 after interference;

[0045] Figure 4 This is the actual test data diagram of Example 2 of the present invention:

[0046] Among them, Figure a is the reflection coefficient at the frequency point of 1942.43MHz before interference; Figure b is the reflection coefficient at the same frequency point of drift tube No. 1 after interference; Figure c is the reflection coefficient at the same frequency point of drift tube No. 2 after interference; Figure d is the reflection coefficient at the same frequency point of drift tube No. 3 after interference; Figure e is the reflection coefficient at the same frequency point of drift tube No. 4 after interference; Figure f is the reflection coefficient at the same frequency point of drift tube No. 5 after interference; Figure g is the reflection coefficient at the same frequency point of drift tube No. 6 after interference;

[0047] The accompanying drawings are marked as follows:

[0048] 1. Vector analyzer; 2. Test connection line; 3. Probe and probe tooling; 31. Probe tooling; 32. Probe; 4. Device under test; 5. Perturbation body and perturbation tooling; 51. Perturbation tooling; 52. Perturbation body. DETAILED DESCRIPTION

[0049] In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the specific implementation methods of the present invention are further described in detail below in conjunction with the drawings and examples. The following examples are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0050] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so as to describe the embodiments of the present application described herein.

[0051] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships described in the embodiments and shown in the accompanying drawings, or are directions or positional relationships in which the inventive product is usually placed when used. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0052] like Figure 1 and Figure 2 As shown, the present invention specifically relates to a method for measuring the uniformity of a microwave resonant cavity field, comprising the following steps:

[0053] Step 1, selecting a suitable perturbator according to the size of the device under test, the device under test is composed of a plurality of beam channels, and the beam channels are composed of a nose cone hole, a nose cone gap and a drift tube;

[0054] In step 1, the perturbation body is made of metal material.

[0055] Step 2: Start the vector network analyzer and perform microwave calibration. The vector network analyzer is connected to the probe through a test connection line, and the probe is placed in the nose cone hole of the device under test through a probe tooling;

[0056] In step 2, the probe fixture is made of polytetrafluoroethylene material to fix the probe in the cavity of the nose cone hole.

[0057] The probe and the nose cone hole maintain the same axial direction.

[0058] Step 3: Use a vector network analyzer to read the parameter S of the device under test at the operating frequency when no perturbation body is placed. 11,u ;

[0059] Step 4: Place the perturbation body and the perturbation body tooling into the nose cone gap of the device under test, and use a vector network analyzer to read the parameter S of the device under the operating frequency when the perturbation body is placed. 11,p ;

[0060] Step 5: Before and after the perturbation, the electromagnetic field at the corresponding position in the space will change, and this change will be reflected in the reflection coefficient S of the electromagnetic field. 11 value;

[0061] By comparing the ΔS of the electromagnetic field before and after the perturbation in step 3 and step 4 11 Value, to judge the change of electromagnetic field;

[0062] Based on the non-resonant perturbation theory, this application proposes a method for measuring the consistency of the electromagnetic field of a multi-beam klystron. The so-called perturbation refers to the use of small metal objects to fill the space that originally had no objects. The distribution of the electromagnetic field will change due to the presence of the metal objects.

[0063] According to the non-resonant perturbation theory, the electromagnetic field at the corresponding position in space will change before and after the perturbation, and this change will be reflected in the reflection coefficient of the electromagnetic field, that is, S 11 Come up, and S 11 This is another quantity that can be detected by a vector network analyzer. Therefore, we can use a vector network analyzer to measure the S of the electromagnetic field before and after the perturbation. 11 The non-resonant perturbation theory gives the change of the electromagnetic field at any point in space before and after the perturbation and its S 11 The relationship between parameter changes is as follows:

[0064] ΔS 11 =S 11,p (ω)-S 11,u (ω)=-jω[k e E 2 -k m H2 ] / P in

[0065] S 11,p , S 11,u are the reflection coefficients before and after the perturbation, respectively;

[0066] ΔS 11 is the difference of the electromagnetic field reflection coefficient before and after the perturbation;

[0067] P in is the average microwave power entering the resonant cavity;

[0068] k e , k m are the shape factors associated with the perturbator, respectively;

[0069] ω is the angular frequency;

[0070] E and H represent the change in electric field and magnetic field at that point, respectively.

[0071] A resonant cavity of a multi-injection klystron usually operates in the fundamental mode TM01, and the resonant cavity is composed of multiple beam channels, namely, a nose cone hole, a nose cone gap and a drift tube.

[0072] Ideally, the processing of these beam channels is exactly the same, so the electromagnetic field distribution formed by the resonant cavity is also exactly the same on these beam channels. The changes in the electromagnetic field that we can make by placing the same perturbation body at the corresponding nose cone gap position of each beam channel should also be consistent, that is, the S 11 The changing values ​​of the parameters should also be consistent.

[0073] On the contrary, if any beam channel is processed inconsistently with other beam channels, the change in the field caused by placing the perturbation body at the corresponding nose cone gap position of the beam channel will be different from the change caused by placing it in other beam channels.

[0074] This difference can be seen through S 11 The difference in the parameter change value is reflected. Therefore, the reflection coefficient S before and after the perturbation body is placed can be measured. 11 The changes in the electromagnetic field of the multi-beam klystron resonant cavity are evaluated.

[0075] Furthermore, when the perturbation body is a cylindrical structure, ΔS 11 Mainly determined by the electric field component. When the measured electric field is higher than the design value, the nose cone gap is reserved to be shorter, and when the measured electric field is lower than the design value, the nose cone gap is reserved to be longer; or

[0076] When the perturbation body is a circular ring structure, ΔS 11Mainly determined by the magnetic field component. When the measured magnetic field is lower than the design value, the nose cone gap is reserved to be shorter, and when the measured magnetic field is higher than the design value, the nose cone gap is reserved to be longer.

[0077] Step 6: When multiple ΔS 11 When the consistency of ΔS is greater than 95%, the device under test is judged to meet the requirements; when one of the ΔS 11 When the consistency is less than 95%, it is determined that the processing of the device under test does not meet the requirements.

[0078] In step 6, the consistency is multiple ΔS 11 Respectively at multiple ΔS 11 compared with the average value.

[0079] Embodiment 1:

[0080] The microwave resonant cavity field uniformity test method is used for measurement. The multi-injection klystron resonant cavity under test is the third harmonic resonant cavity of the 650MHz klystron, and the theoretical design value of its electromagnetic field frequency is 1942.43MHz. In the test system, the vector network analyzer used is KEYSIGHT E5071C. According to the test method, the vector network analyzer is connected to the probe through the test connection line. The probe is inserted into the probe fixture to form a probe and fixture assembly, and then the probe and fixture assembly are inserted into any nose cone hole on one side of the test cavity.

[0081] The sweep frequency range of the vector network analyzer is set to 1932MHz-1952MHz, and the number of measurement points (scanning points) is 1601. In the S11 measurement mode of the vector network analyzer, the electromagnetic field resonance frequency point of the cavity is obtained to be 1942.43MHz, and the value S of the electromagnetic field reflection coefficient before perturbation is obtained at this frequency point. 11,u is -0.6847dB, such as Figure 3 As shown in Figure a”.

[0082] Then the perturbation body is installed in the perturbation body fixture, and the perturbation body and fixture components are inserted into the 6 nose cone gaps on the other side of the measurement resonant cavity in turn, and the electromagnetic field reflection coefficient S after perturbation at the frequency point of 1942.43MHz is obtained respectively. 11,μ,1 =-0.6515dB, S 11,μ,2 =-0.6534dB, S 11,μ,3 =-0.6513dB, S 11,μ,4 =-0.6534dB, S 11,μ,5 =-0.6535dB, S 11,μ,6 =-0.6524dB. The measurement results are as follows Figure 3 As shown in Figures b to g.

[0083] Then calculate the ΔS of each reentrant structure according to the formula 11 value, and obtain ΔS 11，1 =-0.0332dB, ΔS 11，2 =-0.0313dB, ΔS 11，3 =-0.0334dB, ΔS 11，4 =-0.0312dBΔS 11，5 =-0.0313dB,ΔS 11，6 =-0.0323dB. Their consistency is 96.57%, 97.51%, 95.95%, 97.20%, 97.51%, 99.38%, all better than 95%, and the results show that the processing and welding accuracy of the third harmonic resonant cavity of the multi-injection klystron meets the design requirements.

[0084] Embodiment 2:

[0085] The microwave resonant cavity field uniformity test method is used for measurement. The multi-injection klystron resonant cavity under test is the third harmonic resonant cavity of the 650MHz klystron, and the theoretical design value of its electromagnetic field frequency is 1942.43MHz. In the test system, the vector network analyzer used is KEYSIGHT E5071C. According to the test method, the vector network analyzer is connected to the probe through the test connection line. The probe is inserted into the probe fixture to form a probe and fixture assembly, and then the probe and fixture assembly are inserted into any nose cone hole on one side of the test cavity.

[0086] The sweep frequency range of the vector network analyzer is set to 1932MHz-1952MHz, and the number of measurement points (scanning points) is 1601. In the S11 measurement mode of the vector network analyzer, the electromagnetic field resonance frequency point of the cavity is obtained to be 1942.43MHz, and the electromagnetic field reflection coefficient S before perturbation is obtained at this frequency point. 11,u The value of is -0.6979dB, such as Figure 4 As shown in Figure a.

[0087] Then the perturbation body is installed in the perturbation body fixture, and the perturbation body and fixture components are inserted into the 6 nose cone gaps on the other side of the measurement resonant cavity in turn, and the electromagnetic field reflection coefficient S after perturbation at the frequency point of 1942.43MHz is obtained respectively. 11,μ,1 =-0.6792dB, S 11,μ,2 =-0.6468dB, S 11,μ,3 =-0.6762dB, S 11,μ,4 =-0.6677dB, S 11,μ,5 =-0.6424dB, S 11,μ,6 =-0.6474dB. The measurement results are as follows Figure 4 As shown in Figures b to g.

[0088] Then calculate the ΔS of each reentrant structure according to the formula 11 value, and obtain ΔS 11，1 =-0.0187dB, ΔS 11，2 =-0.0511dB, ΔS 11，3 =-0.0217dB, ΔS 11，4 =-0.0302dBΔS 11，5 =-0.0555dB,ΔS 11，6 =-0.0505dB. Their consistency is 49.34%, 65.17%, 57.26%, 79.68%, 53.56%, 66.75%, all worse than 95%. The results show that the machining and welding accuracy of the third harmonic resonant cavity of the multi-injection klystron does not meet the design requirements.

[0089] A test device for microwave resonant cavity field uniformity, comprising a vector network tester, a test connection line, a probe and a probe tooling, a device to be tested, a perturbation body and a perturbation body tooling;

[0090] The probe is assembled in the nose cone hole of the device to be tested through a probe fixture. The probe fixture is made of polytetrafluoroethylene material and has a convex structure, which plays a role in fixing the probe and positioning it in the nose cone cavity.

[0091] The perturbation body is assembled in the nose cone gap of the device under test through a perturbation body fixture, and the perturbation body fixture is made of polytetrafluoroethylene material and has a convex structure, which plays a role in fixing the perturbation body and positioning it in the nose cone cavity;

[0092] The vector network tester is connected to the probe via the test connection line.

[0093] The device can test multi-injection klystrons of various structural types, such as high-power and high-efficiency klystrons.

[0094] Furthermore, the perturbation body is a metal material with a cylindrical, annular or cage-like structure.

[0095] Furthermore, the probe fixture and the perturbation body fixture are respectively arranged coaxially with the drift tube to ensure the accuracy of the measurement.

[0096] The above embodiments are only specific implementation methods of the present invention, which are used to illustrate the technical solutions of the present invention rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the aforementioned embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the aforementioned embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the protection scope of the present invention.

Claims

1. A method for measuring the uniformity of a microwave resonant cavity field, characterized in that: The following steps are involved: Step 1, selecting a suitable perturbator according to the size of the device under test, the device under test is composed of a plurality of beam channels, and the beam channels are composed of a nose cone hole, a nose cone gap and a drift tube; Step 2: Start the vector network analyzer and perform microwave calibration. The vector network analyzer is connected to the probe through a test connection line, and the probe is placed in the nose cone hole of the device under test through a probe tooling; Step 3: Use a vector network analyzer to read the parameter S of the device under test at the operating frequency when no perturbation body is placed. 11,u ; Step 4: Place the perturbation body and the perturbation body tooling into the nose cone gap of the device under test, and use a vector network analyzer to read the parameter S of the device under the operating frequency when the perturbation body is placed. 11,p ; Step 5: Before and after the perturbation, the electromagnetic field at the corresponding position in the space will change, and this change will be reflected in the reflection coefficient S of the electromagnetic field. 11 value; By comparing the ΔS of the electromagnetic field before and after the perturbation in step 3 and step 4 11 Value, to judge the change of electromagnetic field; Step 6: When multiple ΔS 11 When the consistency of ΔS is greater than 95%, the device under test is judged to meet the requirements; when one of the ΔS 11 When the consistency is less than 95%, it is determined that the processing of the device under test does not meet the requirements.

2. The method for measuring the uniformity of a microwave resonant cavity field according to claim 1, characterized in that: In step 1, the perturbation body is made of metal material.

3. The method for measuring the uniformity of a microwave resonant cavity field according to claim 1, characterized in that: In step 2, the probe fixture is made of polytetrafluoroethylene material to fix the probe in the cavity of the nose cone hole.

4. The method for measuring the uniformity of a microwave resonant cavity field according to claim 3, characterized in that: The probe and the nose cone hole maintain the same axial direction.

5. The method for measuring the uniformity of a microwave resonant cavity field according to claim 1, characterized in that: In step 5, the relationship between the change of the electromagnetic field of the device under test before and after being perturbed is as follows: ΔS 11 =S 11,p (ω)-S 11,u (ω)=-jω[k e BY 2 -k m H 2 ] / P in S 11,p , S 11,u are the reflection coefficients before and after the perturbation, respectively; ΔS 11 is the difference of the electromagnetic field reflection coefficient before and after the perturbation; P in is the average microwave power entering the resonant cavity; k e , k m are the shape factors associated with the perturbator, respectively; ω is the angular frequency; E and H represent the change in electric field and magnetic field at that point, respectively.

6. The method for measuring the uniformity of a microwave resonant cavity field according to claim 5, characterized in that: When the perturbation body is a cylindrical structure, ΔS 11 Mainly determined by the electric field component. When the measured electric field is higher than the design value, the nose cone gap is reserved to be shorter, and when the measured electric field is lower than the design value, the nose cone gap is reserved to be longer; or When the perturbation body is a circular ring structure, ΔS 11 Mainly determined by the magnetic field component. When the measured magnetic field is lower than the design value, the nose cone gap is reserved to be shorter, and when the measured magnetic field is higher than the design value, the nose cone gap is reserved to be longer.

7. The method for measuring the uniformity of a microwave resonant cavity field according to claim 1, characterized in that: In step 6, the consistency is multiple ΔS 11 Respectively at multiple ΔS 11 compared with the average value.

8. A testing device using the method for measuring the uniformity of a microwave resonant cavity field according to claims 1 to 7, characterized in that: Including vector network tester, test connection line, probe and probe tooling, device under test and perturbation body and perturbation body tooling; The probe is assembled in the nose cone hole of the device under test through a probe tool; The perturbation body is assembled in the nose cone gap of the device under test through a perturbation body tooling; The vector network tester is connected to the probe via the test connection line.

9. The device for measuring the uniformity of a microwave resonant cavity field according to claim 8, characterized in that: The perturbation body is a metal material with a cylindrical, ring or cage-like structure.

10. The device for measuring the uniformity of a microwave resonant cavity field according to claim 8, characterized in that: The probe fixture and the perturbation body fixture are respectively coaxially arranged with the drift tube.

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